The present invention relates to a carrying system and a carrying method for positioning and carrying a frame of a semiconductor device or the like.
In fabricating a semiconductor device, a carrying system for carrying the frame of an IC is employed. The carrying system is used with a processing unit such as a laser marker for marking the package of a semiconductor device. In recent years, the integration degree of semiconductor devices has increased. In addition, many types of semiconductor devices are now fabricated. Thus, a carrying system for carrying semiconductor devices must not only cope with various types of semiconductor devices, but also control the positional deviation of a lead frame being carried.
FIG. 1 shows a schematic top view of a conventional carrying system.
As shown in FIG. 1, a carrying system 11 is provided with a pair of carriers 12a and 12b. The carriers 12a and 12b are set at the same height. The carriers 12a and 12b are provided with holders 18a and 18b, respectively. In addition, the carriers 12a and 12b are provided with motors 19a and 19b for moving the holders 18a and 18b, respectively. Magazines 15 and 16 are provided between the carriers 12a and 12b. One magazine 15 accommodates a lead frame 17.
The carrying operation of the frame 17 of the semiconductor device is controlled by a controller (not illustrated) as described below. First, the controller moves one holder 18a from a standby position (position shown in FIG. 1) toward the lead frame 17 disposed in the magazine 15, to hold one side of the lead frame 17. At this time, the holder 18a holds the left side of the lead frame 17 with respect to the moving direction. The controller moves the holder 18a by driving the motor 19a to carry the lead frame 17 to a processing position 14 along a carrying line L. At the processing position 14, a processing unit (not illustrated) processes the frame 17. After processing of the frame 17 is completed, the controller moves the holder 18a to thereby carry the frame 17 to the magazine 16. After moving of the frame 17 to the magazine 16 is completed, the controller moves the holder 18a on the carrying line L to a standby position.
While the holder 18a moves the magazine 16 from the processing position 14, the other holder 18b moves another frame 17 in the magazine 15 to the processing position 14. At this time, the holder 18b holds the right side of the frame 17 with respect to the moving direction. After the frame 17 is processed by the processing unit, the holder 18b moves the frame 17 to the magazine 16. At this time, the holder 18a returns to the initial position to hold the next frame 17 in the magazine 15. Thus, the carrying system 11 carries the frames 17 alternately using the two holders 18a and 18b. The alternate carrying decreases the time between processing of one frame 17 and processing of the next frame 17, thereby improving the throughput of frame carrying.
However, the following problem occurs when a clamping operation of the lead frame 17 is performed. As shown in FIGS. 2A to 2C, the holder 18a rotates a movable damper 21 against a fixed damper 20 to hold the lead frame 17. When the lead frame 17 is deflected, the position of the lead frame 17 is deviated leftward in FIG. 1 (direction perpendicularly intersecting the carrying line L) because the movable damper 21 pushes the lead frame 17. Thus, the lead frame 17 is moved to the processing position 14 while having a positional deviation.
Similarly, when the holder 18b holds the lead frame 17, the position of the lead frame 17 deviates rightward. The directions of the positional deviations of the lead frame 17 caused by the holders 18a and 18b are opposite to each other. Therefore, the range in which the lead frame 17 is position-deviated from the processing position 14 is equal to a value obtained by adding the positional-deviation value due to the carrier 12a and the positional-deviation value due to the carrier 12b. For example, when assuming that the positional-deviation values due to the carriers 12a and 12b are roughly the same, the range in which the lead frame 17 can be position-deviated at the processing position 14 is twice as large as the positional-deviation values due to each carrier 12a and 12b. As the range in which the lead frame 17 can be position-deviated increases, it is necessary to further expand the range for detecting the position of the frame 17 to perform an alignment of the lead frame 17 at the processing position 14. Such expansion of the detection range lowers the accuracy for performing alignment of the lead frame 17 at the processing position 14.
Referring to FIG. 3, a stream mark 22 of resin used for sealing a semiconductor chip or a part of a runner may be left on the lead frame 17. Therefore, the position for clamping the frame 17 is further deviated or the frame 17 cannot be securely held due to the resin.
It is an object of the present invention to provide a carrying system and a carrying method capable of reducing a positional deviation value without decreasing the throughput of frame carrying.